Attendees speak to each other during cocktail hour at the national tea party convention in Nashville, Tennessee. Photograph: The Washington Post/Washington Post/Getty Images

America's disparate army of angry ­conservatives assembled under one roof yesterday at the first national tea party convention in Nashville, amid controversy over an opening speech which preached bigotry bordering on racism.

Up to 600 delegates from all over the US descended on the cavernous Gaylord hotel to plot a strategy on how to take back the country from the perceived threat of the Obama administration. Sporting a shirt made from the Stars and Stripes, Tim Peak from Arizona said he had travelled so far because it was "time for the silent majority to stand up and start speaking".

But amid talk about fiscal conservatism and the "subversive threat" of the green movement, there was also a strong undercurrent of a cultural bigotry which previously had been kept to the margins of the tea party phenomenon.

Tom Tancredo, a former Republican congressman from Denver in Colorado who ran for president in 2008, devoted most of his opening speech on Thursday night to illegal immigration. He said the fabric of US society had been eroded by the "cult of multiculturalism", "Islamification", and large numbers of immigrants who did not want to be Americans.

In his most incendiary comment, he invoked the segregationist methods of the southern states, saying that Obama had been elected because "we do not have a civics, literacy test before people can vote in this country". Southern segregationist states used to prevent black people having the vote by setting them restrictively difficult qualification tests, a historical allusion lost on few of the delegates present.

Tancredo went on to call on delegates to launch a "counter-revolution" that would "pass on our culture based on Judeo-Christian principles. Whether people like it or not, that's who we are."

That remark received a standing ovation from the audience.

The convention, called the Tea Party Nation by its organisers in a reference to the Boston Tea Party of Anglo-Saxon colonists opposed to British taxation, seeks to build on the organic, internet-fuelled groundswell of popular anger against mounting government spending that erupted a year ago, prompting alarm and consternation to both Republican and Democratic establishments.

The movement has been keen to avoid accusations it is motivated by racism towards the country's first black president. Mark Skoda, one of the convention organisers, said of Tancredo's speech – "I would have preferred he didn't use that form of words."

The convention has been dogged by controversy even before it opened with some denouncing its $549 (£350) ticket price and criticising it as an attempt to hijack a bottom-up phenomenon for commercial gain. There was evidence of money-making activities. For $89.99, delegates could buy pendants of tea bags made from semi-precious stones and silver, and there were plenty of T-shirts on sale with slogans such as "I'll keep my freedom, my guns and my money" and "Annoy a liberal – use facts and logic".

The spirit of the Birthers, people who believe that Obama is an alien imposter, was also represented. Jack Smith, from Ellijay in Georgia, said he feared "that perhaps we have elected somebody to office that may not be a legal American citizen".

Steve Milloy, who runs a global warming denier website, junkscience.com, delivered a speech denouncing environmentalism as the "greatest threat to America now and in the future".

Amid such a ragbag of phobias, paranoia and principles, one unifying force was support for the former vice-presidential candidate Sarah Palin, who will speak to the convention at its close tonight.